(1) Field of the Invention:
This invention relates to an improved drilling pipe and drilling pipe connector system for use with a downhole electric motor. More specifically, the invention relates to a drilling pipe made from a bundle of rods or wires which also serves as an electrical conductor for the downhole motor.
(2) Description of the Prior Art
Commercial drilling for oil and gas, whether it be on land or offshore, usually involves the use of a rotary drill bit attached to the end of a drilling pipe string suspended from a drilling rig at the surface of the earth. By turning the drilling pipe at the surface, the drill bit at the bottom of the hole rotates and performs the desired drilling operation. Various alternatives to the traditional concept of rotary drilling have been suggested with limited degrees of commercial acceptance. For example, it is generally known to suspend a downhole motor on the end of the drilling string which drives the drill bit. Such a process can occasionally be used competitively particularly in shallow drilling operations where changing the drill bit is unnecessary. However, such techniques are not considered commercially attractive in moderate to deep drilling applications. One problem associated with the use of a downhole motor is the inability to conveniently deliver electrical current to the motor via electrical conductors suspended down the central core of the drill pipe. The nature of this problem can be more readily appreciated when one considers that during the drilling operation the drilling pipe must be occasionally removed from the well to replace the drill bit, place casing, and/or for other related operations. In order to do this, each section of the drilling pipe must be disassembled, but the presence of a continuous cable running from the surface down to the motor makes this task virtually impossible. The presence of the electrical cables also creates problems when a directional survey tool or the like is to be sent down the center of the drilling string. And the fact that it is critical that drilling mud be continuously circulated down the drilling string and back up the annulus between the string and the well bore during drilling makes the mere presence of the electrical cables a risk that is unacceptable in most drilling operations. In principle, these enumerated problems associated with the use of a downhole drill motor are equivalent to the reasons that make hard wire data transmission from downhole instrument packages (the so-called contemporary "measurement while drilling" techniques) an impractical approach to a very desirable end result.